Windows OS Heap Problems

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These explanations apply to Allegro Common Lisp, which is the underlying software used by Pathway Tools. Pathway Tools may require a large amount of computer memory (RAM) to run some commands, to access large PGDBs, or just to start up. The data used by Pathway Tools is stored in a location called "the heap". When Pathway Tools is started it tries to reserve one large block of memory for its heap, probably around 700MB. If it cannot reserve this much memory, that value is automatically lowered. In such a case you may see a message of the form

Temporarily scaling back lisp reserved region from x to y bytes

where x should be around 700MB and y is smaller. This is not an error in itself and Pathway Tools should continue to work.

Another possible error message is something like

lisp heap being relocated by yyyyy bytes

in that case, Pathway Tools is starting up, and this relocation operation — typically caused by a misconfigured Microsoft DLL — may take more than a minute. A typical culprit is Service Pack 2 which hasa DLL that is not relocatable in memory. This problem should not befatal, please wait for Pathway Tools to start up. Microsoft provides a hotfix for Service Pack 2, and you will have to contact themto download and install it.

In other cases, you may see an error message of the form

Error: An allocation request for x bytes caused tenuring and a
       need for y more bytes of heap. The operating system will
       not make the space available because the address space reserved
       for the heap could not be increased.

The error message may vary, but if it contains the “heap could not be increased”, then it is a fatal error and you need to apply one or more of the following remedies. (Please do them in this order)

• Check to see how much RAM and virtual memory you have. This can be done by going to the Windows Control Panel (usually from the start menu/settings), selecting "System" and then the "General" panel. This panel should show the amount of RAM. If it is less then 256MB, it may not be possible to run Pathway Tools with some PGDBs. Preferably it is 1GB or more (over 1000MB). If it is less, you can try to increase the virtual memory by going to the "Advanced" panel, then to the "Performance" section. You should see the amount of virtual memory currently selected. If it is less then 400MB, it should be increased to at least 700MB.
• Try to close down all other unneeded applications. This should reduce memory usage. The Windows Task Manager may help you to determine which applications are using large amount of memory. (The Task Manager is available by right-clicking the task bar, usually located at the bottom of your screen, then selecting it from the menu.)
• You should restart Pathway Tools after doing the previous two steps. If the heap problem persists, try applying the following ...